Pulmonary function parameters and use of bronchodilators in patients with cystic fibrosis*

OBJECTIVE To analyze pulmonary function parameters and pharmacodynamic response to a bronchodilator, as well as the prescription of bronchodilators, in cystic fibrosis (CF) patients. METHODS This was a retrospective cohort study involving patients 6-18 years of age, diagnosed with CF, and followed at a referral center between 2008 and 2010. We evaluated only those patients who were able to perform pulmonary function tests (PFTs). We analyzed FVC, FEV1, and FEF25-75%, expressed as percentages of the predicted values, prior to and after bronchodilator tests (pre-BD and post-BD, respectively), in 312 PFTs. Repeated measures ANOVA and multiple comparisons were used. RESULTS The study included 56 patients, divided into two groups: those whose PFT results spanned the 2008-2010 period (n = 37); and those whose PFT results spanned only the 2009-2010 period (n = 19). In the 2008-2010 group, there were significant reductions in post-BD FEV1 between 2008 and 2010 (p = 0.028) and between 2009 and 2010 (p = 0.036), as was also the case for pre-BD and post-BD FEF25-75% in all multiple comparisons (2008 vs. 2009; 2008 vs. 2010; and 2009 vs. 2010). In the 2009-2010 group, there were no significant differences between any of the years for any of the variables studied. Among the 312 PFTs, significant responses to the bronchodilator occurred in only 24 (7.7%), all of which were from patients for whom no bronchodilator had been prescribed during the study period. CONCLUSIONS In the CF patients studied, there was loss of pulmonary function, indicating progressive lung disease, over time. The changes were greater for FEF25-75% than for the other variables, which suggests the initial involvement of small airways.